The PM plan is complete on paper. Why doesn’t it get done?
Most treatment plants have a PM plan. The problem is rarely the plan itself; it is the gap between the plan and the work that can actually be done this week.
The Waiotech team··5 min read
Almost every treatment plant we visit has a preventive maintenance plan. Sometimes it is a tidy spreadsheet with “interval” and “last done” columns, sometimes the booklet the manufacturer shipped with the equipment, and sometimes a table drawn up for an audit years ago that still hangs on the maintenance room wall. On paper, everything is covered: blowers monthly, sludge pumps quarterly, scrapers every six months.
But when we ask “was the PM on blower 2 done this month?”, the answer is usually a pause. Maybe it was done, maybe it slipped, maybe it was done and never written down. This note is about that gap: why a plan that is right on paper does not get carried out, and what makes it workable.
A plan is not work
The first reason is simple: a PM plan is a commitment, not a job. “Lubricate the blowers monthly” does not tell anyone which blower, this week, with which oil, by whom and following which procedure.
In most plants, the translation from plan to work happens in the maintenance supervisor’s head. On Saturday morning they glance at the table, mention a few items to the technicians and keep the rest for “when things are quieter”. As long as that supervisor is there and their memory holds, the system more or less works. The moment they take leave, the shift changes or a big failure pulls everyone away, the plan quietly falls behind.
The fix is to make every due date of the plan visible as a specific item: “Monthly PM, aeration blower 2, due 12 October”. That item needs a state: recognised, turned into a work order, deferred or skipped. When every due date is a record, it can no longer disappear quietly.
A PM plan has to turn into a list of specific jobs every week; otherwise it is just a good table.
Ready work is not the same as scheduled work
The second reason is that being due is not the same as being ready. Say the quarterly PM on return sludge pump 2 is due this week. What does it take?
- The seal kit, or at least the gaskets, must be in the store.
- Pump 1 must be in service so pump 2 can be taken out.
- The electrical team must be available for isolation.
- The work procedure must be clear, not “the usual”.
If any of these is missing, the job will not happen, even though it is on the weekly schedule. Many PM programmes fail exactly here: every due job goes on the week’s schedule, half of them don’t get done, and the next week the same list comes back with a few more items. After a few weeks, nobody trusts the list.
The planner needs to see which jobs are actually ready and why the others are not. “Part not in stock”, “standby pump under repair”, “permit not issued yet”. Those reasons belong on the job itself, not in a conversation in the corridor.
Deferral should be a decision
In practice, not every PM job gets done on time, and there is no point pretending otherwise. Sometimes deferring a job is the sensible call: bar screen 2 is under repair, so bar screen 1 cannot also be stopped for service. That deferral is fine. The problem is when it happens silently.
A good deferral has three parts: a reason, the person who decided, and a new date. “Bar screen 2 under repair; do after it returns; decided by Ms Ahmadi.” When a deferral is recorded that way:
- The commitment is not erased; the job still exists and has a new date.
- Six months later, it is clear why that PM was late.
- If a failure happens, you can see whether repeated deferrals played a part.
Skipping works the same way. If a blower is out of service and its PM makes no sense this month, it should be set aside with a reason, not simply left undone.
The calendar is not always the best interval
Part of what makes PM ineffective comes from the plan itself. Many intervals are calendar-based because a calendar is the easiest thing to write in a spreadsheet. But equipment that runs irregularly is not well served by a calendar.
A standby blower that runs a few hours a month does not need monthly lubrication. A filter backwash pump that starts at full load several times a day, on the other hand, may need service sooner than its calendar interval. For equipment like this, running hours, number of starts or a reading such as vibration are better triggers.
A plan whose due dates come from real readings follows how the equipment is actually used, and is taken more seriously for it.
A history that is useful later
The last reason is that even when PM is done, little remains that is useful later. “PM done” in a spreadsheet column says very little. What was seen? What colour was the oil? What was the vibration? Was a part replaced?
PM without recorded results is just a tick. PM with readings, observations and findings recorded gradually builds a picture of the equipment. When three PMs in a row on blower 2 note “bearing temperature slightly higher than usual”, the next failure can hardly be called “sudden”.
A short checklist for a plan that gets done
If we had to put all of this in a few lines:
- Every due date is a record, with a clear state: recognised, turned into a work order, deferred, skipped.
- Readiness is seen separately: parts, standby equipment, team and permit, before a job goes on the week’s schedule.
- Deferral and skipping have a reason and a decision-maker, and do not erase the commitment.
- The interval fits how the equipment runs: calendar for some, readings for others.
- PM results are recorded, not just “done”.
A good PM plan is not one that never falls behind. It is one where, at any moment, you can see where things stand and why.